MAPREC for control of the consistency of production of type-3 poliovirus vaccine live oral (OPV) was completed in FY 98, and results were presented to the WHO Expert Committee on Biological Standardization in October FY 99 to consider as a recommended preliminary test preceding neurovirulence tests in monkeys and as an acceptable alternative to monkey testing for type-3 OPV. Reference materials (standard cDNA and reference type-2 poliovirus) were prepared for the WHO Collaborative Study of MAPREC as a test for consistency of production of type-2 OPV. The reference materials were validated by performing multiple tests at CBER and then ampouled and labeled at the National Institute for Biological Standards and Control, UK. Two other samples of type-2 OPV to be included as unknowns in the WHO Collaborative Study were also tested at LMD. LMD prepared an SOP and a Technical Manual for distribution to all participants of the WHO MAPREC Study of type-2 OPV. Type-2 OPV samples containing increasing amounts of mutant poliovirus were tested by the standard WHO Monkey Neurovirulence Test (MNVT) to evaluate the role of selected mutations in experimental neurovirulence. The results suggested that none of the mutations commonly thought to be virulent for monkeys was actually virulent, regardless of the amount present in the preparation; that finding confirmed the observation that no available commercial batch of type-2 OPV has ever been found to be consistently unacceptable by MNVT. Reference preparations of cDNA and poliovirus needed to develop a MAPREC test for type-1 OPV were also prepared and are being validated. The MAPREC test for type-1 OPV is being optimized to include in the final phase of the WHO Collaborative Study of MAPREC for Improved Control of the Consistency of Production of OPV. The project will be continued in FY 00.